Problems idling :(

sms_sms · Two Stroke Sniffer Joined: 16 Sep 2005 Karma :

Hi guys, it's been a long time - haven't had a bike for a few years!
I need to suck some knowledge out of your brains if you dont mind... Laughing

I've got a chinese 125 (yes I know Rolling Eyes

- but it is one of the better ones) and recently have developed idling issues.

It was a gradual problem i.e. the last few times I rode it I had to keep kick starting it a load of times to stop it dying and get it to keep running until it basically wouldn't start up one day.

I have cleaned the carb with carb cleaning spray, adjusted the tappets, changed the spark plug for a new one, changed the oil, installed an in-line fuel filter, and put a bit of ispropyl alcohol in the tank to stop anything icing up. Battery is fine at 12.5V. And I swapped the stock air box for a K&N style cone filter while I was there Smile

Fast forward to yesterday.. Shocked

It ran for a fair while, 5-10 mins but then stalled so I restarted it, didn't seem to be any problems then.
Took it for a spin and after a while it starting having problems when I pulled the clutch in or stopped and you could hear it start to die so I had to keep revving it to stop it dying luckily I got home Very Happy

The thing is, the idle problems seem to be alot worse when the engine is warm :S
Checked the spark plug after the test run and it was grey/brown.

Any ideas guys?

Update: Ran again, ran fine for about 5 mins then died and continued to die when restarted. Ran without fuel cap, didn't make a difference. Seems to be a problem when it's warmed up to a certain point. Weird... Confused

P. · Red Rocket Joined: 14 Feb 2008 Karma :

adjusted carb for that cone filter you added??

chip · Two Stroke Sniffer Joined: 01 Feb 2010 Karma :

remove that inline fuel filter and try again

sms_sms · Two Stroke Sniffer Joined: 16 Sep 2005 Karma :

Yep, plug is a nice browny colour. How would removing the filter change anything? There's enough fuel getting through.
It revs fine its just the idling thats the problem.

slyrob · Traffic Copper Joined: 03 Jan 2010 Karma :

Have you checked the choke cable/assembly?
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Gawain · Nitrous Nuisance Joined: 06 Dec 2008 Karma :

You could try adjusting the mixture screw, Iv found its very sensitive when the airbox is fiddled with.
Mixture screw is under the carb nearest to the engine vertically orientated and a pain to get to. Use a stuby screw driver. Turn it in all the way gently counting the turns, remember this figure. Reset back.
Warm bike up properly and adjust mixture screw in/out until the idle is at its smoothest/fastest.

sms_sms · Two Stroke Sniffer Joined: 16 Sep 2005 Karma :

I've adjusted the mixture screw to its best Smile

I even turned up the idle screw to about 2.5k but it cut out when it got warm again so it's not a blockage in the carb or jets and the choke assemblys fine as I inspected it when it was off.
To be honest I think it's either the valves (which I've adjusted) and the mileage is about 500 miles so I don't think it's that, or its a faulty electrical component.
Does anyone know of an electrical component that might work fine but stop working properly when its warm?

sms_sms · Two Stroke Sniffer Joined: 16 Sep 2005 Karma :

Never mind folks, looks like it was the tappets. Can't believe they closed up so much over 500km!